The home secretary told MPs that allowing the extradition of the self-confessed computer hacker would breach his human rights after experts concluded the Asperger’s-sufferer would be at a high risk of suicide.

Mr McKinnon’s mother Janis Sharp said: ‘Thank you Theresa May from the bottom of my heart – I always knew you had the strength and courage to do the right thing.’

Ms Sharp added that her son could initially not speak when he learned the news.

‘It’s so emotional,’ she told a news conference. ‘We’ve done it. We’ve won for the little person.’

Mr McKinnon, 46, from Wood Green, north London, is wanted in the US over what has been described as the ‘biggest military hack of all time’.

Although Mr McKinnon has admitted the hack after his arrest in 2002, he insists he was only looking for information on UFOs.

Mrs May said it was now up to director of public prosecutions Keir Starmer to decide whether Mr McKinnon should stand trial in the UK.

‘Mr McKinnon is accused of serious crimes. But there is also no doubt that he is seriously ill,’ she said.

‘He has Asperger’s Syndrome, and suffers from depressive illness. The legal question before me is now whether the extent of that illness is sufficient to preclude extradition.

‘After careful consideration of all of the relevant material, I have concluded that Mr McKinnon’s extradition would give rise to such a high risk of him ending his life that a decision to extradite would be incompatible with Mr McKinnon’s human rights,’ she continued.

‘I have therefore withdrawn the extradition order against Mr McKinnon,’ Mrs May added to cheers and a round of applause in the Commons.

Before coming into government, Conservative Party leader David Cameron and his Liberal Democrat counterpart Nick Clegg both opposed sending Mr McKinnon to the US.

Home secretary Theresa May (Picture: PA)

Gary McKinnon’s mother Janis Sharp (Picture: PA)

Mr McKinnon’s local MP David Burrowes, who had threatened to resign as a parliamentary aide if his constituent was extradited, said: ‘Today is a victory for compassion, and pre-election promises being kept.’

The Tory MP continued: ‘Can I congratulate the home secretary for saving my constituent Gary McKinnon’s life today? Can I also praise the tireless campaigning of Gary’s mother, Janis Sharp, and the huge public support?’

Shami Chakrabarti, director of human rights charity Liberty, said: ‘This is a great day for rights, freedoms and justice in the United Kingdom.

‘The home secretary has spared this vulnerable man the cruelty of being sent to the US and accepted Liberty’s long-standing argument for change to our rotten extradition laws.’

Ms Chakrabarti added: ‘Extradition should prevent fugitives escaping – not allow for Britons like Gary to be parcelled off around the world based on allegations of offences committed here at home.

‘This campaign, led by Gary’s fearless mother, united lawyers, politicians, press and public from across the spectrum in the cause of compassion and common sense.’

In preventing Mr McKinnon’s extradition Mrs May also called for a forum bar to be introduced for extradition proceedings, effectively taking away such powers from the home secretary.

Mr McKinnon was arrested in 2002 and then again in 2005, with an order for his extradition made in 2006 under the 2003 Extradition Act.

Three applications for a judicial review into his case followed, as well as scrutiny of the supposedly one-sided UK-US extradition treaty, although Sir Scott Baker found the treaty was balanced and fair in an independent review conducted last year.